1. Field of the Invention
The present invention relates to a method of fabricating gold nanostructures using electroless displacement plating, and gold nanostructures fabricated thereby.
2. Description of the Prior Art
Conventional methods for fabricating nanostructures include electron beam lithography, nano-imprint lithography, focused ion beam lithography, electrochemical deposition, etc.
Electron beam lithography is a process of fabricating nano-sized patterns using electronic energy, in which an electron beam emitted from an electron gun is focused with an electromagnetic lens and is precisely deflected and scanned, thereby processing a resist. In the subsequent process, the resist is developed and the substrate is wet or dry etched, like a general semiconductor process. This method enables the fabrication of patterns having a size of a few nm, but has a disadvantage in that, because focused nano-sized beams are scanned one at a time, too much time is required to pattern a large area, making mass production difficult.
Nano-imprint lithography is a process of patterning a polymer resin by UV or heat, in which a stamp having a pattern protruding from the surface thereof is required for patterning. In order to fabricate the stamp, electron beam lithography and dry etching are generally used. The nano-imprint lithography process enables the fabrication of patterns having a size of several tens of nm, but has disadvantages in that patterns are distorted due to thermal expansion resulting from the difference in material between the stamp and the substrate and in that the application of high pressure is required.
Electrochemical deposition is a process of forming a metal coating layer using electrical energy. It uses an electrochemical reaction. Specifically, when the metal (steel plate) to be plated is negatively charged and placed in a plating solution and an electric current is applied thereto, a metal ion in the plating solution moves to the negative electrode. This process is easily performed, but has a disadvantage in that it is difficult to form a gap at a desired position.
Plating processes are broadly classified into two: electroplating in which the rate of plating is controlled in proportion to the intensity of voltage; and electroless plating the rate of plating is controlled according to the difference in reduction potential from a seed metal and to reaction conditions.
Electroless plating refers to forming a coating layer of a desired metal on the surface of interest by applying an electric current to an electrolyte solution containing a metal ion. Electroplating is a process which is applied to various products, including electronic parts, fancy goods, industrial products, etc. The electroplating is advantageous in that the reaction rate is high, but is disadvantageous in that it is difficult to fabricate nanostructures uniformly on a large area.
Meanwhile, previous studies on the fabrication of gold nanostructures include a method of fabricating gold nanostructures by applying external voltage (Biosensors and bioelectronics 26 (2010) Detection of effect of chemotherapeutic agents to cancer cells on gold nanoflower patterned substrate using surface-enhanced Raman scattering and cyclic votammerty) (J. Raman Spectrosc. 2011, 42, pp. 986-991, SERS study of Ag nanoparticles elelctrodeposited on patterned TiO2 nanotube films), and a method of fabricating gold nanostructures using other media, including a micelle templates and surfactants (Nanotechnology, 22 (2011) 265705, Gold nanorods with finely runable longitudinal surface plasmon resonance as SERS substrates).